Catalytic oxidation of naphthalene



ill

' hitherto.

Patented Nov. 20, 1928.

UNITED STATES 1,692,126 PATENT OFFICE.

ALPKONS O. 'J'AEGER, OF GRAFTON, PENNSYLVANIA, ASSIGNOB TO THE SELDEN COM- PANY, or PITTSBURGH, rruvnsrnvama, a

CATALYTIC oxrnarron or NAPHTHALENE.

No Drawing. Original application filed November 24, 1928, Serial No. 150,623.

cation filed December 12,

The present invention relates to the processes for the catalytic oxidation of naphthalene in the vapor phase to intermediate products, such as phthalic anhydride, etc.

In the past naphthalene has been oxidized in the vapor phase to phthalic anhydride, sometimes with the concurrent production of alphanaphthaquinone and maleic acid, by passing vapors of naphthalene over catalysts containing metals of the fifth and sixth groups of the periodic system, such as vanadic oxide, molybdenum oxide, and the like. These processes usedhitherto have had 'considerable success but are open to the very serious disadvantage that it ispractically impossible to so control the reaction as to obtain hi h percentage yields with commercially f easible outputs. The oxidation of naphthalene to alphanaphthaquinone pre' sents great difiiculty because of the relative instability of this product and has not hitherto been successfully carried out with oxide catalysts. The oxidation to phthalic anhydride has had more success as the product is more stable but in this case also the reaction tends to go too far, producing considerable amounts of total combustion as well as smaller amounts of maleic acid. When the reaction goes too far the'amount of heat evolved is enormously increased which very seriously affects the control of the reaction and necessitates the use of very powerful cooling means, such as boiling metal baths and the like. If the catalyst is sufiiciently diluted or the reaction sufiiciently damped. to prevent large amounts of total combustion, serious trouble arises due to the fact that part of the naphthalene will not oxidize.

Even when the average temperature of the contact mass is controlled, there is a serious tendenc of the catalyst hitherto used to form zones 0 local over-heating due to the excessive activity of the catlysts and perfectly homogeneous dilution has not been feasible The present invention overcomes partly or wholly most of the disadvantages set out above and consists broadly in the oxidation of or anic compounds, especially in the vapor phase, in the resence of catalysts or contact masses in whlch part or all of the catalyticallyactive elements are present in the form of two component zeolites, that is to safy, base exchanging polysilicates which are ormed cations of the zeolite,

CORPORATION 01 DELAWARE.

Divided and this appli- 1927= Serial No. 239,617.

by methods analogous to those of the natural or artificial water-softening zeolites which are usually either aluminum double silicates or aluminosilicates. Amon the natural zeolites are nepheline, leucite, eldspars, and the like, and numerous artificial aluminum zeolites have been prepared for water-softening means. In general, two com onent zeolites are prepared by the reaction 0 two classes of 3 components, i e. silicates and either metaltion are characterized by a highly porous,"

honeycomb like structure and show high resistance to melting, recrystallization and poisoning. The zeolites may be used either diluted or undiluted, but for best results in the catalytic oxidation of naphthalene I prefer to use diluted zeolites in which the diluent bodies are preferably homogeneously mixed with the zeolite components. The invention, of course, is not limited to the use of these diluted .zeolite catal sts which constitute the preferred embodiment thereof and undiluted zeolites may be used or they may be mixed mechanically with diluents or impregnated into porous diluents.

The catalytic elements may be present in zeolites in four different forms, namely in the zeolite nucleus, changeable form, as one of the exchangeable as an anion which may form with the zeolite a salt-like body, and finally in the case of diluted zeolites in the diluent, which may either be itself a catalyst or may be impregnated with catalytic components. Obviously, of course, catalytic elethat is to say, in non-exments may be present in more than one of these forms in a single catalyst and a large number of such combinations are possible.

In addition to the elements which are actual catalysts, certain other elements, while not themselves catalysts, or atleast not strong catalysts, appear to exert a.- marked effect on the catalytic components themselves and may be termed activators. The SiO,, group notably appears to possess marked activating line compounds powers and it is one of the advantages of the present invention that the same zeolite structure or framework which permits the fine or molecular distribution of catalytic atoms or groups in a highly porous, physically homogeneous product, also supplies the activating SiO group.

It isan advantage of the zeolites of the present invention that by suitable treatment with acid gases the exchangeable alkali of the zeolites may be transferred into non-alkawhich tend to stabilize the oxidation of naphthalene and which are formed in intimate homogeneous association with the catalytically active components. Stabilizers may also be added to zeolites in a pre-formedstate. Ido not claim in this inventionthe use of such stabilizers generally, this forming the subject of my co-pending application No. 196,393, filed June 3, 1927. In the present application, however, all such stabilizlng means mixed with or formed on zeolite catalysts are included as specific fea- 'tures of the present invention.

It is an advantage of the present invention that an enormous number of different catalysts can be prepared, all sharing the extremel advantageous physical structureof the zeolites and being provided with suitable silicious activating components. The chemical combination of the zeolite molecule is not accurately known because it is im ossible to obtain the molecular weight 0 the product without disintegrating it. Without limiting the present application to any theories of zeolite constitution, I am of the opinion that the zeolite molecules existing in actual products are of extremely hi h molecular weight because I have found t at catalytic components can be introduced and chemically combined in the zeolite nucleus in substantially any desiredproportions. This indicates that the molecule is not of low weight, as otherwise, the lawof molecular proportions would at once become apparent. It is, of course, possible that the zeolites are not of high molecular weight, but consist of a solid solution of different simple zeolites. The underlying chemical reasons are, however, not important, the main thing being that it is possible to introduce catalytic components in almost any nents for any particular igo desired proportions into the zeolite molecule in non-exchangeable form so that it is possible to prepare catalysts having just the right proportions of one or more catalytic comporeaction, a feature which is of enormous value to the catalytic chemist. A

, The nucleus or non-exchangeable portion of the zeolite molecule is ordinarily considered to consist of metal oxides, usuall amphoteric metal oxides, combined with Si 2 to form an a"""on which appears to behave as a single group and cannot be split by ordinary chemlikum, manganese, iron,

' which may the relatively large number of catalytically active metal oxides may be introduced into this portion of the zeolite nucleus either in the form of their metallates or in the form of neutral or acid salts or complex compounds. In some cases, it may be necessary to introduce the de sired metal in a stage of oxidation different from that which it is to finally possess in the finished zeolite and effect suitable oxidation or reduction during zeolite formation. The following elements in suitable stages of oxidation in which they possess the desired amphoteric properties may be included in the metal oxide portion of the zeolite: copper, silver, gold, bismuth, beryllium, zinc, cadmium, boron, aluminum, rare earths, titanium, zirconium, tin, lead, thorium, niobium, antimony, tantalum, chromium, molybdenum, tellurium, tungsten, uranium, vanadinickel, cobalt, osmium,

arsenic. They may be introduced singly or in mixture in any desired proportion and may be in the form of simple or complex ions.

When naphthalene is oxidized beyond the stage of alphanaphthaquinone, it is generally assumed that the reaction takes place in stages and it may be desirable to incorporate different catalysts into the same zeolite, one catalyst favoring one sta e and one another, and it is an advantage of the present invention that it is possible to incorporate several different kinds of catalysts into the same zeolite, thereby effecting an extraordinarily ho mogeneous mixture due to the molecular dispersionof the different catalyst components throughout the zeolite mass. Insome cases it maybe necessary to carry out a plurality of different types of reactions, thus, for example, naphthalene may be oxidized to phthalic anhydride and carbon dioxide split off to produce benzoic acid. The reaction, be carried out in two stages using zeolite catalysts in one or both, may also be carried out 1n a single stage in which a combination catalyst may be used and it is an advantage of the present invention that such a combination catalyst can be prepared as a physical, and in many cases chemically homogeneous product.

I havefound that the oxidation of naphthalene, particularly to phthalic anhydride,

li t

is most effectively carried out in the pres- 1/ ferred type of catalyst for producing phthalic anhydride.

'For the production oflower stages of alphanaphthaquinone it is sometimes advantageous to eliminate the vanadium or to eliminate almost all of it in order to prevent too vigorous an oxidizing effect which might destroy unstable alphanaphthaquinone and such zeolite catalysts, which may contau tain little or no vanadium in the nucleus, are

included in the present invention.

The vanadium which is present in the nu cleus may be in the form of trivalent, tetravalent or pentavalent vanadium, and for some catalysts it is very desirable to introduce into the nucleus part of the vanadium in one state of oxidation and part in another. A similar possibility exists with respect to other metal elements which are capable of introduction in different stages of oxidation and particularly with elements of the fifth and sixth groups, such as: niobium, antimony, tantalum, chromium, molybdenum, tungsten, bismuth and uranium.

The SiO, portion of the zeolite nucleus does not necessarily have to consist solely of $0,, although for many catalysts the activatin or stabilizing efi'ect of the SiQ radical ma es this desirable. In other cases, it may be desirable that part of SiO should be substituted by a suitable acidic oxide which is capable of zeolite formation and in this way components of catalytic, activating or stabilizing effect can be introduced, such as, for example, one or more of the acidic oxides of: phosphorus, sulfur, tin, titanium, tungsten, chromium, niobium, tantalum, uranium,

molybdenum, arsenic, antimony, vanadium, etc. The present invention, however, does not include recesses of oxidation in which a base exchange catalyst is used which does not contain SiO Such catalysts do not come under the definition of the word zeolite as used in the present invention, and for the subject-matter of the co-pending app ication, Serial No. 171,727 filed February 28, 192

Additional catalytic, activating or stabilizing components can be introduced by base exchange. Examples of such components are the simple or complex ions of: lithium, sodium, potassium, ammonium, copper, rubidium, caesium, silver, gold, beryllium, magnesium, calcium, zinc, strontium, cadmium, barium, mercury, aluminum, thallium, titanium, zirconium, tin, antimony, thorium, vanadiam, bismuth, chromium, uranium, manganese, cobalt, iron, palladium, platinum.

After theneolite is formed, it may thenbe caused to react with compounds havin suitable anions which form with the zeolite odies which behave in many ways as if they were salts. It is not hown whether actual salts are formed, since, of course, the products are for the most part not soluble in water, and the invention is, therefore, not limited to any particular chemical theorylof combination. Among the anions which can be caused to react with the zeolites under "suitable conditions to form salt-like 'bodiesare the acidic oxides of the following elements: vanadium, tungsten, *uranium, chromium, molybdenum, manganese, tantalum, niobium, antimony, selenium, tellurium, arsenic,p hosphorus, bismuth, sulfur, chlorine, platinum. and boron. These elements may be introduced in the form of simple or complex anions, such as for example, ferro and ferricyanogen, sulfocyanogen, metal cyanogen, and ammonia complexes may also be caused to react with the zeolites.

A single anion or a plurality of anions can becaused to react either simultaneously or successively.

It will thus be apparent that there are four groups within the zeolite body, the non-exchangeable nucleus with its metal oxide and acidic oxide components, the exchangeable cations and the anions which form with the zeolite salt-like bodies. The effect of a particular catalytic element is not necessarily the same when it is present in the nucleus as when it is present, for example, as an exchangeable cation, and it is thus possible to form innumerable combinations which per- -mit the catalytic chemist to'produce catalysts having characteristics exactly adjusted for the particular oxidation which he desires to carry out. a

In all cases, the catalytic components are distributed throughout the zeolite molecule in a state of molecular subdivision and apparently are protected to a large extent by the surrounding zeolite skeleton or framework so that they are far less subject to poisoning and to other deleterious influences.

The products are also for the most part highof heat since most of the reactions are highly exothermic. \Vhile in certain cases, therefore, it is possible to use undiluted zeolite catalysts in organic oxidations, and the present invention lncludes such use, I prefer, for the most part, to use diluted zeolites, which, in genera are of more satisfactory catalytic activity and which also usually are cheaper to produce, as, in general, the diluent bodies.

used are less costly,v than the zeolite components themselves.

Ahnost any inert or activating body can be used as a diluent. Preferably, however, I

use porous diluents and articularlydiluents which are rich in silica in order to enjoy the valuable stabilizing and activating properties of the SiO group, which has been mentioned in connection with the zeolite structure itself. The usei of. diluents rich in silica. is particularly important. A few of the many pos- .sible diluents are the following: kieselguhrs of all kinds, particularly natural or treated powdered zeolites, either natural or artificial,

' powders of rock, stones, tuflfs, trass, lava and powders,

similarv volcanic products which are frequently highly porous, green sand, glauconite, pulverized slag wool, cements, sand, silica gel, pulverized earthen ware, fullers earth, talc, glass powder, pumice meal, asbestos, graphite, quartz meal and powders of various minerals rich in quartz, metal metal oxides and salts, particularly tungstates, vanadates, chromates, uranates, manganate's, cerates, molybdates, etc. Some of these diluents are inert, others contain silica and may be considered as activators, and still others are themselves catalytically active. 1 It should be noted that when an inert body is sufficiently finely divided, as, for example, when the average particle size is less than 60 microns, the diluent possesses surface 'energy which'increases the absorption and diffusion speed and porosity of the final prod not and, therefore, may be consideredas a kind of physical catalyst or-activaton The diluents may be incorporated in many ways. For example, they can be mixed wit one or more of the zeolites before formation. The zeolite gel immediately after formation may be mixed with diluents or a combination of these processes can be carried out. Zeolite components or the finished gel may be impregnated into diluents, usually" porous diluents and the like. When the'diluent is mixed with components or gel before harden-' ing and in some cases, where the zeolite components are impregnated into the diluent in considerable amount, the resulting product is a physically homogeneous whole, in which the diluent particles are uniformly distributed throughout the zeolite framework,

and for many purposes this type of product is'the most satisfactory, although the invention is in no sense limited thereto. It should be understood that diluent bodies may be imregnated with various catalytic components Eefore incorporation in the zeolite and many highly active catalysts can be produced in this way. The impregnation may be by precipi tation, reduction, oxidation or by the introduction of colloidal suspensions, or solutions of the catalytic component. In some cases,

catalytic components may also be caused toreact-with the diluent or to form therewith chemical compounds, although this is not as common, sincemost of the diluents are relatively inert chemically.

Many possible types of diluted zeolites and processes are fully described in a large number of examples in the application of, J aeger & Bertsch, Serial No. 95,771, filed March 18, 1926, and any of the processes and products therein described may be used to produce catalysts of the present invention.

Instead of incorporating catalytic components chemically combined with the zeolite,

a non-catalytic zeolite may be used-as a car-' rier or diluent for catalytic components im pregnated into the fine pores of a natural or artificial zeolite. In such a case, the zeolite acts as an activator by reason of its physical structure and its high content of silica. In-

stead of impregnating catalytic components into a finished zeolite, it isalso possible to incorporate insoluble catalytic bodies with the components of the zeolite during formation so that the. catalytic particles are uniformly and homogeneously distributed throughout the zeolite structure, but are, of course, in most cases, not in a state of molecular division as in the case of catalytic components chemically combined with the zeolite. Another important class of catalysts is produced by impregnating inert or activating diluent bodies with catalytic components and then incorporating these impregnated diluents with a zeolite which is not itself catalytically active. In all cases, the advantages of the zeolite structure are obtained and the particular catalyst to be used in any given reaction will be determined by the conditions of that reaction.

In some cases, the homogeneous diluted zeolite may.'advantageously be in the form of a film or coating on massive carrier granules or fragments and such contact masses are included in the present invention. The mas- I sive carriers may be inert,- activating or themselves catalytic, as, for example, when certain catalytic metal alloys are used. Certain contact masses using metal fragments hot spots which are so series in naphthalene oxidations.

The remarkable effectiveness of the zeolite catalysts of the present invention for the oxidation of naphthalene is probably due to a number of features such as the advantageous porous, physical structure of the catalysts, their high resistance to the temperatures which obtain in the reactions, the activating power of the silica present, etc. Without limiting the invention to any theories, however, I am of the opinion that one of the most important reasons for the effectiveness of the catalysts lies in the fact that the zeolite framework separates the individual catalyst particles or catalyst molecules from each other so that at no point in the catalyst is there a large amount of active catalytic material present. There is, therefore. not such a tendency to the formation of local hot spots due to too violent reaction. I have found that in naphthalene oxidations, the intermediate products are more or less unstable, particularly in the presence of the catalysts which cause their formation, and at elevated temperatures. I am, therefore, of the opinion that the far reaching isolation, and, to a certain extent, insulation ofone catalyst particle or molecule from the other prevents the decomposition of the intermediate products formed because they are almost immediately brought out of contact with the. catalyst and the heat evolved is uniformly distributed throughout the zeolite. framework.

For the oxidation of naphthalene, the presence of an alkali is sometimes undesirable, especially where it is desired to obtain phthalic anhydride as the reaction'product, and the alkalinity of most "zeolites is preferably neutralized, and in many cases it is desirable to have the product distinctly acid. This neutralizing of alkali can be efiected in several ways. In the first place, the zeolite reaction can be caused to take place in solutions which are not strongly alkaline. The resulting products have a comparatively low base exchange power and perhaps there is formed a mixture of zeolites and non-base exchanging polysilicates. The physical structure, however, is-similar to that of the zeolites which possess strong base exchanging powers,

and for many purposes the catalysts are just as efiective. In some reactions, this diminished alkalinity may be suflicient to permit the reaction to be carried out satisfactorily. In other cases, where even this degree ofalkalinity is undesirable, the zeolite may be treated with'acids to form salt-like bodies which are acid in their nature, the product, of course, varying with the amount of acid which is caused to react with the zeolite. I have found, however, that in the case of most catalysts, it is desirable to subject the product to treatment with an acid gas at temperatures of from 400500 6., in the resence of air or other oxidizing medium; uch acid gases may be S0 S0 halogens, oxides of nitrogen, etc., and the process is described in my prior applications Serial No. 48,001, filed August 3, 1925, and Serial No. 48,002, filed Aug. 3, 1925.

This procedure in the case of most zeolite catalysts has the additional advantage that the acid gas reacts with the alkali present to form salts of the alkali forming metals, which, as has been pointed out above, act as stabilizers and tend to prevent the reaction becoming uncontrolled and proceeding to total combustion with serious losses in yield. This treatment also appears in most cases to enhance the activity of the zeolite and possibly this is due to physical changes which may ta e place. In general, it should be clearly understood that all zeolite catalysts undergo certain secondary chemical and perhaps physical transformations during catalysis, and therefore, the use of the word zeolite or zeolite body in the claims is not intended to limit the present invention to processes in which the zeolite identity of the catalyst remains throughout the reaction. The nature of these secondary transformations "is not definitely known, and therefore, in the claims the word zeolite is used to cover zeolites which have undergone secondary changes during catalysis as a result of preliminary treatment with acid gases. In all cases, however, the macroscopic, and in many cases, the microscopic, physical structure of the zeolite catalyst remains unchanged.

For the most part, zeolite catalysts of the present invention are sufficiently porous, but in some cases it may be desirable to still further increase this porosity. In such cases, soluble, volatile or combustible fillers, may be incorporated into, the zeolite and later on removed, leaving .c'orresponding hollow spaces and still further increasing the porosity of the product.

In most cases, the zeolite catalysts are ofsufiicient mechanical stren th to withstand all the ordinary strains to w ich they are subjected during catalysis. In some cases, however, particularly where the zeolite is diluted with a very large amount of diluents, the mechanical strength may be insuflicient for catalytic purposes. In such cases, the product ma be washed with waterglass, particularly dilute solutions of waterglass and a certain amount of surface silicification is there-- j by effected. At the same time, thistreatmentgglli may be used to neutralize or change the dcgree of alkalinity of the product. i

In the following specific examples a number of representative zeolite catalysts are described, but the invention is, of course, not limited to the catalysts specifically enumerated, nor to the'methods of formation of the catalysts therein described, although an attempt has been made to illustrate as many as possible of the representative methods. In general, however, any suitable processes-for the formation of the zwlites may be used, such as for example in the processes described in the co-pendin applications of Jaeger & Bertsch, Serial 0. 91,229, filed Feb. 27, 1926 Serial No. 95,771, filed Mar. 18, 1926, and Serial No. 100,116, filed Apr. 6,1926.

- Example 1.

An artificial carrier is prepared by mixing B. potassium waterglasq solution and forming into tablets. The tablets are first treated with 18.2 parts of V 0 either in the form of 10% potassium vanadate solution or a hot saturated ammonium vanadate solution. The impregnation is effected by spraying the soluv tions onto the tablets, the latter being continuously turned over. and heated to a temperature suflicient to effect evaporation of the water. A little potassium silicate solution is then cautiously sprayed onto the tablets in the same manner. This solution may preferably be made by diluting a 33 B. solution containing about 24 parts of SiO,, with glass a nascent state. The product is then treated with air containing carbon dioxide at a temperature below 100 C. and then'with gases containing SO at 400 C. A contact sulfuric acid process begins almost at once and the S formed tends to destroy the alkalinity bothof the artificial carrier and of the zeolite film. 7

Instead of anartificial carrier, fragments of quartz, Celite, uartz filter stones, diatomaceous stones or ints may be used.

' Naphthalene vapors mixed with a large and heated tom-70 C.

then permitted .solved'up in 5 N. potassium excess of-air, for exam le, in the ratio of 1 :30 by weight are passe over the catalyst at 350-420 (land a good yield of alphanaph thaquinone is obtained.

Emmi/p102.

The following mixtures are prepared:

(1) 42 parts of SiO in the form of a 33 Be. potassium waterglass solution are diluted with 200 parts of water and 70-parts of Celite are stirred in. I

(2) 18.2 arts of V 0 are dissolved in a concentrate caustic potash solution to form a 10% potassium vanadate solution.

I (3) 5 parts of aluminum oxide aredishydroxide solution. to form potassium aluminate.

Mixures 1, 2 and 3 are poured together 10% sulfuric acid is to run in with vigorous agitation until the whole mass solidlfies to angel which must remain alkaline to litmus. is is then sucked, well pressed and dried at temeratures below 100 C. whereupon the mass is broken into'fragments and sprayed with sulfuric acid of a strength of l part concentrated sulfuric acid .til a sample submerged in water in a test tube and warmed shows an acid reaction to congo. The product is an acid sulfuric acid salt-like body of the zeolitein which vanadium and aluminum are present in non-exchangeable form.

The catalyst is calcined with air at 300 I 400 C. and a mixture of naphthalene vapor and air in proportions of 1:10 to 1:15 is passed over the cataylst at 380-450 G. 1 An almost theoretical yield of 'phthalic anhydride is obtained.

' Example 3.

60 parts of Celite or a mixture of 40'parts Celite and 240 parts finely broken quartz, pumice, glass, neutral silicates or asbestos fibres are suspended in 300 parts of water. To this slurry is added a solution of potassium vanadate containing 14 parts of V,,O

dissolved in 5 N potassium hydroxide solution containing 12 parts of 100% KOH. The

in a solution which is "acidto "congo. The

suspension is then heated for one-half an hour at C. with vigorous agitation so that the V 0 which is present incollodial solution is completely precipitated. The mixture is then sucked and the cake washed with glass solution of30B. are diluted water until the wash water is no longer acid to congo, whereu'ponthe cake is dried and comminuted. parts. of potassiumwaterwith 24-40 parts of water and kneaded into the impregnated carrierdescribed above, the kneading bein continued "until the brown color of the V 6 has disappeared. The product is then formed into fragments and constitutes a diluted zeolite, in which V 0 is present in non-exchangeable form.

. In a similar manner, a zeolite can be prepared by substituting an equivalent amount of potassium vanadite for the potassium vanadate, in which case the zeolite will contain tetravalent vanadium. A mixture of the solutions may also" be used, producing a to 5 parts of water un-.

zeolite containing both tetravalent and pentavalent vanadium in non-exchangeable form.

The catalyst is then sprayed with 510% sulfuric orphosphoric acid to form the socalled salt-like body, which is then heated with air at 400 C.

Naphthalene vapors and air in the proportion of from 1:10 to 1:30 are passed over the catalyst at 370450 C. and an excellent yield of. is obtained.

A still better catalyst naphthalene to tained if the zeolite is sprayed with a 3% vanadyl sulfate solution instead of" sulfuric or phosphoric acid solutions. After the calforthe oxidation of cination with air at a temperature of 450 C.

this catalyst will give excellent, yields of ghthalicanhydride under the reaction con itions described above and can be loaded to almost double the capacity of 1y described catalyst.

60 parts of Celite or'mixture of 40 parts of Gelite and 40 parts of/ finely divided quartz or other ample 1, are suspended in 300 parts of water. A solution-of Cpotassium vanadate or vanadite is forme by dissolving 14 parts of V 0, or V O 'in 5 N potassium hydroxide solution containing 12 parts of 100% KOH, and the solution is stirred into the suspension. 100 parts of potassium waterglass sophthalic anhydride is ob-- phthalic anhydride of high purity the previousdiluents as described in Ex- I of a thick gel, care being taken that the gel remains alkaline to litmus. 'This is then sucked and the cake dried at temperatures below 100% C. whereupon it is brokeninto fragments which are then sprayed with sufficient 510% sulfuric acid so that a sam le suspended in water gives an acid reaction to congo. Instead of spraying with dilute acid, the dried zeolite may be calcined at temperatures of '0500 C. with oxidizing gases containing 7% of S0 The catalyst obtained by either method is excellent for oxidation of naphthalene to. alphanaphthaquinone in the vapor phase, a mixture of naphthalene vapors and air in the proportion of from 1: 30 to 1:45 by weight being passed ver the catalyst at a temperature of 370-420 C.

The same catalyst can be rendered suitable for the oxidation of naphthalene tohthalic anhydride by washing the careful y prepared zeolite-body three or four times with 200 parts of Water, the further treatment with acids or acid gases being the same. This wash treatment'removes excess alkali and the catalyst thus produced tends to oxidize naphthalene to phthalic anhydride. This is an excellent example of the effect of salts of alkaliforming metals as stabilizers, since, of course, the excess alkali is transformed into the corresponding salt by treatment with dilute acids or calcining with acid gases. The stabilizing or damping effect ofthe alkali metal salt is sufiicient to change a phthalic anhydride catalyst to one which favors'the next lower stage of'oxidat-ion, namely, alphanaphthaquione.

l I Example 5.

- parts of Celite or a mixture of 40 parts of Celite and 40 parts of finely divided quartz or other diluents described-in Example 4, are mixed with 100 parts of potassium waterglass solution of 33 B. diluted with three times the amount of water. 14 parts of vanadic acid are then reduced by means of sO -in a boiling aqueous suspension, acidi fled with sulfuric acid until the blue vanadyl sulfate solutionis formed. This solution is then added to the mixture with vigorous agitation, maintaining the waterglass suspension alkaline to litmus throughout. A ge forms which is'sucked in the usual manner and treated as described in the foregoing examples. If the zeolite is washed several times cining, the catalyst then causes the oxidation of the naphthalene to phthalic anhydride when naphthalene vapors and air are passed over it under the reaction conditions described inthe foregoing examples,

Similar catalysts can also be obtained by forming salt-likebodies with the zeolite or by introducing other cations by base exchange.

14.4 parts of molybdic oxide in the form of potassium molybdate aredissolved in 400 I parts of water, into which solution 60 parts of. kieselguhr are thoroughly stirred. The molybdic oxide is then precipitated in a fine state of subdivision in the kieselguhr by adding a suitable amount of 10% sulfuric acid. 125 parts of a 33 Be. otassium waterglass solution are added wit vigorous agitation and the mixture warmed to 7 07 5 C. Complete precipitation is effected by adding about parts of a 10% ammonium sulfate solu .tion. The gel formed is sucked, washed with Example 7.

'A gel of a vanadium mute, as described in Example '3, rior' to treatment with acid to form a salt-1i e body is kneaded with a gel of molybdenum zeolite as described iii-Ex ample .6. The mixed zeolite obtained is then-fi treated with gases containing 57% of sulfur?- dioxide and air at 450 C. until the'alkalinity is neutralized; The catalyst is an excellenti one for vapor phase oxidation of naphthalene to fphthalic anhydride under conditions described in the foregoing examples.

- E'axample'8.

' A mixed zeolite as described in Example 7 is washed with adilute' potassium waterglass solution prepared by diluting a 33 B. solution with 4 volumes of waterfand is then subjected .to the sulfur dioxide treatment described above. The catalystproduced is ex'- cellent for the oxidation of naphthalene to" .alphanaphthaquinone. and produces onl a small amount of phthalic anhydride... his illustrates the effectiveness of certain salts'o f, alkali-fonning metals as stabilizers for oxi dation catalysts, since, of, coursej,f.the-SQ,:' gases and mr reacting with the additional amounts of potassium waterglass'produce' adiof water and 5 parts of concentrated sulfuric ditional amounts of P um liris'ulfate,v with 200 parts of water before dryi I I I I I I acid are added. The vanadic oxide is then reduced in the usualmanner at an elevated temperature with S0, to produce the vanadyl sulfate. The excess acid is then neutralized by "a normal potassium hydroxide solution and 140 parts of 33 B. potassium waterglass solution diluted with 300 parts of water and then added tothe blue vanadyl sulfate solution, the water-glass being permitted to flow in with vigorous agitation. A gel forms at once which is pressed, washed several times with small amounts of water, totaling 300 parts, and dried at temperatures below 300 C. After drying, the zeolite is ground with parts of ,Celite earth and moistened with a solution of 20 parts of potassium bisulfate and 100- parts of water. The moistening is made uniform and the mass then formed to granuleswhich are, then dried and calcined at 400-450 C; in a stream of air to which, if desired, ti-6% of SO may be added.

Naphthalene vapors mixed with air in the proportion of from 1:10 to 1:15 are passed over the catalyst at 380440 C. Yields of phthalic anhydride amounting up to 85% of the theoretical may be obtained.

E sample 10.

Natural or artificial zeolites in the form in which they are available commercially are digested fwith 5% sium chloride, lithium chloride, rubidium chloride, caesium chloride or mixtures in order to'replace the sodium by base exchange. The zeolites are dried and 250 parts y volume are sprayed with a 23% ammonium van-adate or ammonium molybdate solution or a mixture of the two at an elevated temp n-attire in order to impregnate thezeolites.

he product is thereafter calcined at 400- 450 C. in astream of air and is then treated the same term rat-ure with a mixture of air and 54% of 0 containing gases, whereupon. the contact sulfuric acid process begins. Air is then blown through until acid vapors are no longer noticeable.

Naphthalene vapors mixed with air in the proportion offrom 1:10 to 1:20 by weight are passed over the catalyst at 370-420 C.

and good yields of phthalic anhydride are ob tained. v

This application is a division of my prior co-pending application, Serial No.-150,623,

iilcd November 24, 1920.

What is claimed as new is:

1. A method of oxidizing naphthalene, which comprises causing vapors of naphthalene admixed with an oxidizing gas-to react in the presence of a catalyst containing a zeolite, y

2. A method of oxidizing naphthalene, which comprises causing vapors of naphtha-- lene admixed with an oxidizing gas to react in. the presence of a catalyst containing a diiuted zeolite. Y

aqueous solutions of potas- 3. A method of oxidizing na hthalene, which comprises causing vapors o naphthalene admixed with an oxidizing gas to react in the presence of a catalyst containing a diluted zeolite having catalytically active diluents.

4. A method of oxidizing naphthalene, which comprises causing naphthalene vapors admixed with an oxidizing gas to react in the presence of a catalyst containing a zeolite, at least part of the catalytically active elements being present in chemical combination with or in the zeolite.

5. ,A method of oxidizing naphthalene, which comprises passing naphthalene vapors admixed with an oxidizing gas over a catalyst containing a zeolite, at least part of the catalytically: active elements being chemically (fiombined in the zeolite in non-exchangeable orm.

6. A method of oxidizing naphthalene,

at least one catalytically active componentof the catalyst containin vanadium.

8. A method of oxi izirig naphthalene, which comprises causing naphthalene vapors admixed with an oxidizing gas to react in the presence of a catalyst containin a zeolite having vanadium chemically com ined in or with. the zeolite.

9. A method of oxidizing naphthalene, which comprises causing naphthalene vapors admixed with an oxidizlng gas to react in the presence of a catalyst containing vanadium chemically combined with a zeolite in non' exchangeable form. A

10. A method according to claim 6 in which at least one of the acid radicals caused to react with the zeolite is catalytically active.

I 11. A method according to claim 6 in which a vanadium containing acid radical is caused to react with the zeolite. to form the salt-like body.

12. A method according to claim 1 in which at least one catalytically active base is chemically combined in the zeolite in exchangeable form.

13. A method of oxidizing naphthalene to phthalic anhydride, which comprises passing naphthalene vapors and air over a catalyst containing a zeolite, the catalyst also contain ing components which favor the oxidation of naphthalene to phthalic anhydride.

14. A method of oxidizing naphthalene to phthalic anhydride, which comprises passing naphthalene vapors with an oxidizing gas over a catalyst which contains a zeolite, the

- ing a zeolite, at least one of the catalytically active components being chemically combined in or with the zeolite. v

16. A method of oxidizing naphthalene to phthalie anhydride, which comprises causing naphthalene vapors and an oxidizing as to pass over a catalyst favoring the old ation of naphthalene to phthalic anh dride, which catalyst contains a diluted zeo ite.

17. A method of oxidizing naphthalene to phthalic anhydride, which comprises causing naphthalene vapors and an oxidizing gas to pass over a zeolite catalyst containing vanadium and'adjusted to favor the productionof phthalic 'anhydride.

9. 18. A. method of oxidizing naphthalene to phthalic anhydride, which comprises causing naphthalene vapors and air to pass over av zeolite catalyst containing vanadium in chemical combination therein or therewith.

19. A method of oxidizing naphthalene to phthalic anhydride, which comprises causing naphthalene vapors and air to pass over a .zeoli te catalyst containing vanadlum-chemically combined in the zeolite in non-exchangeable form.

20. A method of oxidizinglnaphthalene to phthalic anhydride, which comprises causing naphthalene vapors and air to ass over a zeolite catalyst containing tetrava ent vanadium chemicall combined in the zeolite in non-exchangeab e form.

Signed at Pittsburgh, Pa, this 9th day of December, 1927.

ALPHONS o. JAEGER; 

